1. Field of the Invention
This invention relates to a method for preparing silicon carbide particles, more particularly to a method for preparing silicon carbide particles having an excellent dispersibility in an electrolytic bath for composite electroplating of metals.
2. Description of the Related Art
As is well known, plated nickel coatings having silicon carbide particles dispersed therein, which are obtained by a composite or joint electrodeposition process, have markedly improved wear-resistance, hardness, lubricity and other physical properties. Therefore, the coatings of this character are being widely used for surface protection of various metal articles, including internal combustion engine cylinders. U.S. Pat. No. 3,904,490 disclosed a method in which sericite is added to the electrolytic bath to improve the dispersibility of the silicon carbide particles therein. However, the addition of sericite will change the viscosity of the electrolytic bath and the content of the silicon carbide in the coating. In practice, the content of sericite in the bath is difficult to detect continuously during the electrodeposition process, thus creating an unknown variable factor of the control of the content of silicon carbide in the bath. Therefore, the quality of the coating is difficult to control.
Japanese Patent Publication No. 57-71812 disclosed a method for preparing silicon carbide particles having improved dispersibility, including washing the silicon carbide particles by an acid solution and removing suspended impurities and the residue acid solution on the silicon carbide particles by a hot alkaline solution. In the hot alkaline solution treatment, ammonia water is under a temperature of 90.degree. to 100.degree. C. This causes an evaporation of ammonia water and a bad smell.